package com.small.nine.wxmp.utils.wx.crypt;

import cn.hutool.core.codec.Base64;
import cn.hutool.core.util.RandomUtil;
import cn.hutool.core.util.StrUtil;
import com.small.nine.wxmp.common.constant.BaseConstant;
import com.small.nine.wxmp.config.WxConfig;
import com.small.nine.wxmp.domain.bean.wx.WxInMsgBean;
import com.small.nine.wxmp.utils.wx.XmlUtils;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.Objects;

/**
 * 微信加解密
 *
 * @author Tencent
 * @date 2021-08-04 10:51
 */
public class WxMsgCrypt {
    /**
     * 公众平台 appID
     */
    private String appID;
    /**
     * 公众平台上，开发者设置的 token
     */
    private String token;
    /**
     * 公众平台上，开发者设置的 EncodingAESKey
     */
    private byte[] aesKey;
    /**
     * UTF_8 字符集
     */
    private static final Charset UTF_8 = StandardCharsets.UTF_8;

    private WxMsgCrypt() {
    }

    /**
     * 初始化
     *
     * @param appID  公众平台 appID
     * @param token  公众平台上，开发者设置的 token
     * @param aesKey 公众平台上，开发者设置的 EncodingAESKey
     */
    public WxMsgCrypt(String appID, String token, String aesKey) {
        if (StrUtil.hasBlank(appID, token, aesKey) || aesKey.length() != 43) {
            throw new IllegalArgumentException("微信公众号配置信息有误");
        }
        this.appID = appID;
        this.token = token;
        this.aesKey = Base64.decode(aesKey);
    }

    /**
     * 初始化
     *
     * @param config {@link WxConfig}
     */
    public WxMsgCrypt(WxConfig config) {
        this(config.getAppID(), config.getToken(), config.getEncodingAesKey());
    }

    /**
     * 将一个数字转换成生成 4 个字节的网络字节序 bytes 数组.
     */
    public static byte[] number2BytesInNetworkOrder(int number) {
        byte[] orderBytes = new byte[4];
        orderBytes[3] = (byte) (number & 0xFF);
        orderBytes[2] = (byte) (number >> 8 & 0xFF);
        orderBytes[1] = (byte) (number >> 16 & 0xFF);
        orderBytes[0] = (byte) (number >> 24 & 0xFF);
        return orderBytes;
    }

    /**
     * 4 个字节的网络字节序 bytes 数组还原成一个数字.
     */
    public static int bytesNetworkOrder2Number(byte[] bytesInNetworkOrder) {
        int sourceNumber = 0;
        for (int i = 0; i < 4; i++) {
            sourceNumber <<= 8;
            sourceNumber |= bytesInNetworkOrder[i] & 0xff;
        }
        return sourceNumber;
    }

    /**
     * 生成 xml 消息.
     *
     * @param encrypt   加密后的消息密文
     * @param signature 安全签名
     * @param timestamp 时间戳
     * @param nonce     随机字符串
     * @return 生成的xml字符串
     */
    private String generateXml(String encrypt, String signature, String timestamp, String nonce) {
        String format = "<xml>\n"
                + "<Encrypt><![CDATA[%1$s]]></Encrypt>\n"
                + "<MsgSignature><![CDATA[%2$s]]></MsgSignature>\n"
                + "<TimeStamp>%3$s</TimeStamp>\n"
                + "<Nonce><![CDATA[%4$s]]></Nonce>\n"
                + "</xml>";
        return String.format(format, encrypt, signature, timestamp, nonce);
    }

    /**
     * 将公众平台回复用户的消息加密打包.
     * <ol>
     * <li>对要发送的消息进行AES-CBC加密</li>
     * <li>生成安全签名</li>
     * <li>将消息密文和安全签名打包成xml格式</li>
     * </ol>
     *
     * @param plainText 公众平台待回复用户的消息，xml格式的字符串
     * @return 加密后的可以直接回复用户的密文，包括msg_signature, timestamp, nonce, encrypt的xml格式的字符串
     */
    public String encrypt(String plainText) {
        // 加密
        String encryptedXml = encrypt(RandomUtil.randomString(BaseConstant.BASE_STRING, 16), plainText);

        // 生成安全签名
        String timeStamp = Long.toString(System.currentTimeMillis() / 1000L);
        String nonce = RandomUtil.randomString(BaseConstant.BASE_STRING, 16);

        String signature = SHA1.getSHA1(this.token, timeStamp, nonce, encryptedXml);
        return generateXml(encryptedXml, signature, timeStamp, nonce);
    }

    /**
     * 对明文进行加密.
     *
     * @param plainText 需要加密的明文
     * @return 加密后base64编码的字符串
     */
    public String encrypt(String randomStr, String plainText) {
        ByteGroup byteCollector = new ByteGroup();
        byte[] randomStringBytes = randomStr.getBytes(UTF_8);
        byte[] plainTextBytes = plainText.getBytes(UTF_8);
        byte[] bytesOfSizeInNetworkOrder = number2BytesInNetworkOrder(plainTextBytes.length);
        byte[] appIdBytes = this.appID.getBytes(UTF_8);

        // randomStr + networkBytesOrder + text + appid
        byteCollector.addBytes(randomStringBytes);
        byteCollector.addBytes(bytesOfSizeInNetworkOrder);
        byteCollector.addBytes(plainTextBytes);
        byteCollector.addBytes(appIdBytes);

        // ... + pad: 使用自定义的填充方式对明文进行补位填充
        byte[] padBytes = PKCS7Encoder.encode(byteCollector.size());
        byteCollector.addBytes(padBytes);

        // 获得最终的字节流, 未加密
        byte[] unencrypted = byteCollector.toBytes();

        try {
            // 设置加密模式为AES的CBC模式
            Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
            SecretKeySpec keySpec = new SecretKeySpec(this.aesKey, "AES");
            IvParameterSpec iv = new IvParameterSpec(this.aesKey, 0, 16);
            cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);

            // 加密
            byte[] encrypted = cipher.doFinal(unencrypted);

            // 使用BASE64对加密后的字符串进行编码
            return Base64.encode(encrypted);
        } catch (Exception e) {
            throw new RuntimeException(e.getMessage());
        }
    }

    /**
     * 检验消息的真实性，并且获取解密后的明文.
     * <ol>
     * <li>利用收到的密文生成安全签名，进行签名验证</li>
     * <li>若验证通过，则提取xml中的加密消息</li>
     * <li>对消息进行解密</li>
     * </ol>
     *
     * @param msgSignature 签名串，对应 URL 参数的 msg_signature
     * @param timeStamp    时间戳，对应 URL 参数的 timestamp
     * @param nonce        随机串，对应 URL 参数的 nonce
     * @param encryptedXml 密文，对应 POST 请求的数据
     * @return 解密后的原文 {@link WxInMsgBean}
     */
    public WxInMsgBean decrypt(String msgSignature, String timeStamp, String nonce, String encryptedXml) {
        // 密钥，公众账号的app corpSecret
        // 验证安全签名
        String signature = SHA1.getSHA1(this.token, timeStamp, nonce, encryptedXml);
        if (!Objects.equals(signature, msgSignature)) {
            throw new RuntimeException("加密消息签名校验失败");
        }

        // 解密
//        return decrypt(encryptedXml);
        return XmlUtils.xmlToBean(decrypt(encryptedXml), WxInMsgBean.class);
    }

    /**
     * 对密文进行解密.
     *
     * @param cipherText 需要解密的密文
     * @return 解密得到的明文
     */
    public String decrypt(String cipherText) {
        byte[] original;
        try {
            // 设置解密模式为AES的CBC模式
            Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
            SecretKeySpec keySpec = new SecretKeySpec(this.aesKey, "AES");
            IvParameterSpec iv = new IvParameterSpec(Arrays.copyOfRange(this.aesKey, 0, 16));
            cipher.init(Cipher.DECRYPT_MODE, keySpec, iv);

            // 使用BASE64对密文进行解码
            byte[] encrypted = Base64.decode(cipherText);

            // 解密
            original = cipher.doFinal(encrypted);
        } catch (Exception e) {
            throw new RuntimeException(e.getMessage());
        }

        String xmlContent;
        String fromAppId;
        try {
            // 去除补位字符
            byte[] bytes = PKCS7Encoder.decode(original);

            // 分离16位随机字符串,网络字节序和AppId
            byte[] networkOrder = Arrays.copyOfRange(bytes, 16, 20);

            int xmlLength = bytesNetworkOrder2Number(networkOrder);

            xmlContent = new String(Arrays.copyOfRange(bytes, 20, 20 + xmlLength), UTF_8);
            fromAppId = new String(Arrays.copyOfRange(bytes, 20 + xmlLength, bytes.length), UTF_8);
        } catch (Exception e) {
            throw new RuntimeException(e.getMessage());
        }

        // appid 不相同的情况 暂时忽略这段判断
//        if (!Objects.equals(fromAppId, this.appID)) {
//            throw new RuntimeException("AppID不正确，请核实！");
//        }

        return xmlContent;
    }
}
